@monopalle I was asking the same questions about Lidgren a few weeks ago on this forum, the differences between tcp/udp etc just like you, I’m also new to network development. I came to the conclusion that Lidgren is good enough for our needs - even for chat. Yes TCP is slower and more reliable between packets, but from my understanding of Lidgren he has done some cleaver stuff in there that you can basically have the same affect as TCP.
_client.SendMessage(outmessage, NetDeliveryMethod.ReliableOrdered);
If you use the “ReliableOrdered” delivery method as in the above example, then this basicalls acts like TCP - so for messages you need to send and ensure they are in order (chat) then use this method - for messages that you don’t mind going missing (e.g. movement?) then use a different delivery method.
Here is the thread I questioned in, SpiceyWolf has also done a library which he offered me:
Hope this helps.